Modeling Dynamic Uniaxial Compression of a Ferrous Alloy in an External Magnetic Field

Author(s):

John D. Clayton

Abstract:

Modeling of dynamic compression of a ferrous alloy with ferromagnetic and weakly paramagnetic phases is undertaken. The constitutive model, published in prior works by the author and collaborators, includes finite strains, nonlinear thermoelasticity, rate-dependent plasticity, and solid-solid phase transformations. Maxwell’s equations for conductors use a quasi-magnetostatic approximation. The present calculations treat a material element as an isotropic mixture of coexisting phases. Deformations and magnetic field are locally homogeneous over phases, but magnetization is not. Phase transition kinetics account for effects of magnetic fields. Previously determined phase transition parameters were obtained for this alloy under mechanically quasi-static, tensile loading. Here, predictions are obtained with these parameters, and with those of pure iron, for boundary conditions mimicking those witnessed in plate impact experiments. Effects of external magnetic fields of strength 2 T on the stress-volume response are predicted to be small. Transition initiation pressures, in contrast, are notably affected by such fields. Different parameter choices impede or promote transitions. Hugoniot predictions are similar to existing data on stainless steels.